Soil respiration and its Q ₁₀ response to various grazing systems of a typical steppe in Inner Mongolia, China

Abstract

Soil respiration was significantly different among the three grazing systems. The average Rs was highest under rest-rotation grazing (1.26 μmol·m^-2·s^-1), followed by grazing exclusion (0.98 μmol·m^-2·s^-1) and year-long grazing (0.94 μmol·m^-2·s^-1). Rs was closely associated with ST, SM, potential substrate and root, and soil microbe activity. The effects of grazing among two grazing systems had generality, but were different due to grazing intensity. The root biomass was stimulated by grazing, and the rest-rotation grazing system resulted in the highest Rs. Grazing led to decreases in aboveground and microbial biomass as well as the loss of soil total nitrogen and total phosphorus from the steppe ecosystem, which explained the negative effect of grazing on Rs in the year-long grazing system compared to the grazing exclusion system. The temperature sensitivity of Rs (Q₁₀) was higher in the rest-rotation and year-long grazing systems, likely due to the higher temperature sensitivity of rhizosphere respiration and higher "rhizosphere priming effect" in the promoted root biomass. The structural equation model analysis showed that while grazing inhibited Rs by reducing soil aeration porosity, ground biomass and SM, it increased Q₁₀ but had a lower effect than other factors. A better understanding of the effects of grazing on soil respiration has important practical implications.